Absorption machines used as chillers and ice makers predate similar duty vapor compression machines by the better part of a century. With the advent of universal electrical usage and, more so, with the introduction of the chlorofluorocarbon refrigerants, vapor compression machines supplanted but did not completely eliminate absorption machines from the marketplace. Since the 1950's, vapor compression machines manufactured to condition room air not only cool in the Summer but heat in the Winter thereby assuming the characteristics of true heat pumps. Heat pumps thus are of two categories: rotary absorption heat pumps (RAHP's) and vapor compression heat pumps (VCHP's).
The conditions which initially heavily favored VCHP's in the marketplace have subsequently been somewhat altered. The world has become more conscientious about conserving energy, especially since the large increase in the price of energy which occurred during the mid 1970's. The economic balance here favors the absorption process, because it can utilize low-grade waste heat efficiently.
Also, with the recent recognition of the destructive behavior of chlorofluorocarbons (CFC's) on the earth's protective ozone layer, the heretofore ideal class of refrigerants for use in VCHP's has been eliminated, thus further tilting the balance in favor of the absorption process.
The RAHP's differ from conventional VCHP's both in their operating cycle and in their construction. The common cycle components in RAHP's and VCHP's are the evaporator and the condenser but thereafter the similarity ends. In the VCHP's, the vapor produced in the evaporator is increased in pressure by means of a mechanical pump and at the higher pressure it is cooled and liquified in the condenser. Subsequently, it is returned to the evaporator in order to complete the cycle. In the RAHP's, the refrigerant vapor produced in the evaporator is absorbed in a deliquescent material located within a component termed the absorber. The diluted deliquescent material is then transferred to a component named a generator within which the refrigerant vapor is separated from the material and its pressure is increased by the application of heat. The vapor at higher pressure is subsequently directed to a condenser wherein it is cooled and liquified before it is returned to the evaporator in order to complete the cycle.
Essentially, the absorber, generator, and deliquescent material or absorbent of RAHP's replace the mechanical compressor of VCHP's. In place of the mechanical energy needed to drive the compressor of VCHP's the RAHP's employ low-grade heat to separate the refrigerant from the absorbent material and, concomitantly, increase the refrigerant vapor pressure in the generator.
In order to capitalize on the advantages accruing to rotation, rotary VCHP's have been built and tested. They have proven to be more compact and quieter in operation than stationary VCHP's. However, rotating seals have compromised hermeticism and market acceptance has not been achieved.
In order to retain object hermeticism and to simultaneously employ waste heat, the rotating VCHP construction disclosed in Doerner U.S. Pat. No. 3,863,454 has been advocated. However, the Doerner design retains its dependence on clorofluorocarbons for the refrigerant and possibly for the boiler power fluid, in addition to requiring a high-temperature heat source for its operation.
It is the general purpose of the present invention to formulate the absorption heat pump process into a rotating unitary construction wherein the properties of rotation are used to simplify the procedure so as to result in the provision of a compact and mechanically simple heat pump unit, thereby enhancing the popularity of the absorption type unit in the marketplace.
It is another important object of the present invention to conserve energy by circumventing the wasteful process of converting the energy in primary fuel to mechanical or electrical energy, which energy subsequently is targeted to operate cooling equipment.
Still a further object of the present invention is the provision of a rotary absorption heat pump unit which is of compact, unitary construction; which is tolerant of changes in air temperature, operating rotational speed and generator temperatures; and which minimizes the undesired occurrence of crystallization of the absorbent solution during operation or down time of the heat pump unit.
Another object of the present invention is to reduce the physical size of RAHP's by constructing their evaporator and condenser components to be concentric and coaxial with the absorber and generally locating them radially outboard from the absorber.
It is a further object of the present invention to improve the efficiency and capacity of RAHP's by formulating a very thin film of absorbent within the absorber of such a thickness and of such a residence time that the absorption process is brought to an optimum completion.